Objective:To investigate the effect of initiator on pulsed Nd:YAG laser in the acid resistance of human teeth in vitro. Methods:A total of 25 enamel-samples and 25 dentine-samples were divided into laser plus initiator (a layer of Beijing black ink) group and laser only group.Each of the two groups was divided into five subgroups.The samples in the 5 subgroups were irritated by Na:YAG laser with an energy(J/cm2) of 0,20,30,40 and 50 respectively. Then all samples were immersed in 0.1 mol/L lactic acid demineralization solutions(pH 4.5) for 48 h at 37 ℃. The concentration of Ca 2+ (?10 -6 g) dissolved in the solution was measured by the calcium selective electrode. Results:Laser of 20-50 J/cm2 decreased the Ca 2+ concerntration in demineralization solution(P0.05).The initiator plus laser of 30-40 J/cm2 decreased the Ca 2+ release of dentine samples than laser only group (P

Objective To explore the best parameters of impulse Nd:YAG laser-aided debonding for ceramic bracket.Methods The removal of ceramic bracket from enamel surface by laser irradiation was investigated in vitro.Fifty-four premolars were used to test the tensile strength and 32 premolars for pulp cavity temperature test.The results were compared according to the laser setting(output power:0,2,3,5 W;time:2,4 s),the average force(830.3,556.5 g) necessary to break the adhesion between ceramic bracket and tooth,the different edible pigment on bracket surface(black or not).Results The bonding strength of ceramic bracket was significantly reduced by laser irradiation,averagely by 48%.The average bonding strenth in the six groups for tensile strength test was of statistical difference(P

Objective To investigate the morphology and bonding of enamel and dentin conditioned by 35% phosphoric acid and pulse Nd:YAG laser.Methods A total of 52 human premolars were selected,40 of which were divided into four groups randomly: group A [enamel treated with 35% phosphoric acid(Scotchbond,3M) for 30 s];group B [enamel treated with pulse Nd:YAG laser(Evlaser Friendly A4 Italy) for 20 s];group C(dentin treated with 35% phosphoric acid for 15 s);group D(enamel treated with pulse Nd:YAG laser for 15 s).The tensile bond strength(TBS) were determined.Except 4 out of 12 human premolars without any treatment,8 were divided into 4 groups and were treated with the method mentioned above.The surfaces of 12 human premolars were observed under SEM.Results The highest TBS was obtained in group A in comparison with the other 3 groups(P0.05).The smear layer on enamel and dentin could be removed after conditioned by both phosphoric acid and pulse Nd:YAG laser.The honeycomb structures were observed on all enamel but less regularly in lased group.Almost all the orifices of dentinal tubules were open in the acid group and sealed or half-sealed in lased group.Conclusion The pulse Nd:YAG laser did not contribute to bonding of enamel,but could improve the bonding of dentin and seal most of the orifices of dentinal tubules,which reduced the harmful stimulation to the dental pulp.

Objective To investigate the effects of pulsed Nd∶YAG laser combined with NaF solution on acid resistance of human dental enamel and dentin in vitro Methods A total of 20 enamel samples and 20 dentin samples were treated with both laser plus NaF, laser only, NaF only, or no treatment(control) Then all samples were immersed in lactic acid demineralization solution(pH 4 5) for 48 h at 37 ℃ The concentration of Ca 2+ (?10 -6 g) dissolved in the solution was measured by atomic absorption spectrophotometry Results In both enamel and dentin samples, the lowest mean Ca 2+ concentration was recorded in laser plus NaF treated group (62 055?5 879,137 474?4 444)?10 -6 g The control samples showed the highest mean of Ca 2+ concentration (143 760?5 443 and 182 726?16 115)?10 -6 g The mean Ca 2+ concentration in laser plus NaF - or NaF - or laser treated group decreased significantly as compared with that in the control( P

Objective To observe the changes in activity of matrix metalloproteinase-2 (MMP-2) in gingival tissue of a chronic periodontitis rat model in normoxia and hypoxia condition, and explore the role of MMP-2 in the development of high altitude periodontal diseases. Methods Thirty-two adult SD rats were randomly divided into 4 groups (8 each): normal control group (N group), normoxia periodontitis group (P1 group), hypoxia control group (H group) and hypoxia periodontitis group (P2 group). The chronic periodontitis rat model was reproduced in P1 and P2 group, and the rats were kept either in normoxia condition or hypoxia condition in a hypobaric chamber in which a condition simulating 5000 meter high altitude was established. Rats without periodontitis in N and H group were treated with the same conditions as control. The activation of MMP-2 in gingival tissue of rats in each group was measured by gelatin zymographic analysis. Results The grey values of activated MMP-2 in N, P1, H and P2 group were 13.72?6.22, 37.23?4.40, 14.45?6.51 and 45.44?4.79, respectively. The value was higher in H group than in N group, in P2 group than in P1 group (P

Objective To evaluate the effect of driving forces similar to those found in dental plaque fluid on the enamel demineralization and ultrastructure of surface layer.Methods The sections of human enamel were exposed to lactic acid solutions with degree of saturation with respect to enamel and degree of saturation with respect to fluoroapatite for 96 h at 25 ℃,using the deionized water as control in the same conditions.Enamel demineralization was monitored using SEM and confocal laser scanning microscopy(CLSM).Results Only was enamel subsurface demineralization detected in solutions with DS_(EN)(0.1-0.3).Enamel mineral loss and micropores of surface layer decreased significantly with increasing DS_(EN) and DS_(FA) values.However,no mineral loss and micropores of surface layer was observed in sections of enamel exposed to solutions with DS_(EN) values of 0.4 and 0.5,which were covered with homogeneous remineralization layer.Conclusion The demineralization driving forces similar to dental plaque fluid under different DS_(EN) and DS_(FA) have significant effects on the surface layer of enamel and the subsurface demineralization process.

Objective To observe the effect of different energy levels of pulsed Nd∶YAG laser irradiation on the changes of NO and NOS levels in ulcer tissue of oral ulcer model.Methods Forty-eight Sprague-Dawley rats were inflicted with oral ulcer,and then randomly and equally assigned to 6 groups,that is,oral ulcer group,1% iodine glycerin group and the rest 4 groups receiving pulsed Nd∶YAG laser irradiation at 1.5 W 40 mJ,1.5 W 60 mJ,1.5 W 80 mJ or 1.5 W 100 mJ(once per day,for 3 consecutive days).The other 8 rats served as normal control.In 24 h after last treatment,4 rats from each group were sacrificed and their cheek pouches were taken out for NO and NOS levels in the mucosal tissue by spectrophotomentry.Ulcer healing were observed 24 h after the last treatment for 8 consecutive days.The efficiency of Nd∶YAG laser irradiation at different powers were evaluated.Results Irradiation groups had significantly shorter healing time compared with iodine glycerin group.Level of NO and NOS activity in 1.5 W 60 mJ and 1.5 W 80 mJ groups was evidently lower than the ulcer group(P

Objective:To observe the clinical effects of extraoral manual reposition approach in the treatment of acute anterior disloca-tion of temporomandibular joint. Methods:98 patients with acute anterior dislocation of temporomandibular joint were divided into 2 groups(n=49) by random digit table and treated by manual reposition through intraoral and extraoral approach respectively. The suc-cess rate, success time, patient pain during treatment, SBP, DBP, HR and patient satisfaction were evaluated respectively. Results:The success rate(95. 92%) and the patient satisfaction rate(76%) of extraoral method group were higher than those of the intraoral method group (81. 63% and 66%);success time(3. 91 ± 0. 55)s and patient pain during treatment(3. 51 ± 0. 25) in extraoral method group were less than those in the intraoral method group[(5. 57 ± 0. 51) s and (6. 6 ± 0. 21)]. The degree of changes of SBP, DBP and HR in extraoral method group were less than those in the intraoral method group(P<0. 05). Conclusion:Extraoral manual reposi-tion approach is more effective than intraoral approach in the treatment of acute anterior dislocation of temporomandibular joint.

Objective To evaluate the odontogenetic ability of first branchial arch cells of E12.5 rats. Methods First branchial arch cells (mandibular process) of E12.5 SD rats were isolated enzymatically and collected. After combined with gelatin sponge, the cells were transplanted into the renal capsule of a rat. The specimen was taken out and evaluated by histological and immunohistochemical methods in 4 weeks after growth in renal capsule. Results The first branchial arch cells with gelatin sponge developed dentin-pulp complex-like structure. Dentin sialoprotein (DSP) was expressed in the newly formed dentin-like structure. The green mineralized matrix was further identified with Masson’s trichrome staining. Conclusion Cells from first branchial arch of E12.5 rats can partially keep genetic signal of tooth growth and form dentin-pulp complex-like structure in renal capsule.

Objective: To observe the effect of hypoxia on changes of proliferation ability of cultured human periodontal ligament fibroblasts (HPLFS) in vitro. Methods: HPLFS were randomly divided into two groups (experimental group and control group) by different oxygen concentrations. The oxygen concentration of control group was 21%. The oxygen concentrations of experiment group were 10%, 5% and 2%. The proliferation ability of HPLFS was detected by MTT colorimetric assay. The cell ultrastructure was observed by transmission electron microscope (TEM). Results: MTT assay results showed that compared with the control group, at the 12 h and 24 h, cell proliferation was enhanced with the hypoxia degree. At 24 h, cell proliferation showed significant differences. At 48 h and 72 h, proliferation of the cultured HPLFS in severe hypoxia group reduced significantly. Observed by TEM, at 24 h, not only the number of mitochondria, rough endoplasmic reticulum but also cell process increased in the cultured HPLFS in severe hypoxia group. At 72 h, the number of lysosome increased and the cell structure degenerated. Conclusion: Long-time severe hypoxia may lower the repair and remodeling abilities of periodontium, which might be one of the important etiological factors of periodontal disease under condition of high altitude.